KW suspension Spring flip thought process
 

I want to first start by saying I'm no expert in road car suspension but I do have quite a bit experience setting up Off road long travel suspension. If you've got something to add here please discuss I really want to get this car setup best as possible.


I'm concerned with the spring rate on my Frs. I think I may have figured out the problem.

My current setup is KW coil-overs setup with the Higher rate spring in the rear(out of box configuration). Compression is up +1 for the front and -2 for the rear. Rebound is Factory for front and rear.

When I go to the track unload all the stuff from the trunk remove floor mats ect.. this car gets light. So light in fact that, the rear end hikes when braking causing the rear of the car to over rotate under trail braking.
Second thing that happens is the car is a bit un compliant in the rear durring the exit on turn 13 at the Roval for instants. Also the car feels a bit unmannered in the rear. I believe this issue is I'm not using all the travel.So to combat this I turn down the compression even more this just seems to amplify the issue with braking and trail braking, in addition to making the car seem more unstable at high-speed. All these issue I believe are stemmed from a over sprung rear.

Flipping the spring will combat the front end dive, make the rear more compliant while allowing higher shock rates used to maintain control also allowing for less agressive rebound valving.( Theory only)


Unfortunately like most people on this board I use my car almost every day. So the down side of just flipping the springs around could be bad. Lets say you work in sales like I do. I usually pile in a laptop, small client file maybe some sample product and a small tool bag. this weights in at over hundred pounds. Not to mention if somebody else is in the car with me. This will quickly load up the rear of the car and make the front end light also causing the rear to become harsh and not a good ride.( This should be the side effect of flipping springs.)

I think the spring choice for this car was done so it could be used everyday not as a track car. This is the overall goal of a manufacture KW suspension is for street and track. In this case the rates suffer at the track.


Enough ranting
Just my thoughts.

I will be flipping my springs for the next event.

Gregg

We are not running the standard or the flipped configuration. I think you should adjust your rear rebound though as it sounds like maybe you are running a little too much in the rear. Is it bouncy over bumps or is it a little harsh?

What kind of tire and what size are you using?

- Andrew

aggreed with drew

think of compression as "adding hydralic spring" to an allready at the edge sprung car. rebound can be used to control the lift under braking and even "tamp down" the rear getting ready for a braking event. switching splings can flip the cars balance too pushing too.....
the KW's are so easy to adjust ride height I would drop the spring perch 3turns too
I am running a flipped setup BUT no rear sway...so it evens out (the car is HELLA low though).
search robispec for pic's

RObi

I did try running more rebound it did help the nose dive but the car got harsher through the rough stuff, also added in some more over steer on exit with power. Almost like the shock is packing up.
I'm on Weds wheels 18x8 with a offset of 45. Tires are Michelin pilot sports 245/35/18, front and rear.

You should keep your rear rebound softer (though not so soft that it's bouncy). That will stabilize the rear. Rear compression is not the issue here (for braking) though a little more front can help. I also suggest option C...changing the front springs while keeping the rears where they are.

- Andrew

Option C may work, Would you suggest the same spring for the front that are on the rear?

We are running 400/400 on our car. It works really well. We can source some springs for you if you are interested along with damper settings that will work with them.

- andrew

All things being equal, running more front spring and less rear bar will not even things out, that will dramatically bias the car towards understeer. If you still have neutral handling, it's because you changed some other variable in addition to the springs and sway bars.

Well, if I know anything about robi's cars it's that they don't understeer.

yes but almost anything you do to the car changes the balance...
going to 245 sticky street rubber changes the equation a bunch.
running the car 3" lower REALLY messes with the weight transfer
http://i240.photobucket.com/albums/f...s/IMAG0060.jpg
(in a good way)
http://i240.photobucket.com/albums/f...s/IMAG0057.jpg
we are slightly narower rear track and 1.5" wider front track than stock. Front roll center is corrected (to allow the rear to transfer weight faster) and front tierods bump steer corrected for the drop and the tubular front lower control arms.
-3.5 front camber and full bump travel front and rear.
http://i240.photobucket.com/albums/f.../rearUpper.jpg
one of the parts that helps this
the car is slightly loose under trailbraking or off throttle turn, in mid throttle gets you to neutral/slightly tight, off throttle to full throttle at apex yields barely loose corner off caught if nessisary (usually the torque loss with RPM increase does this) with a light twitch of the steering wheel we will probably soften the front spring one step to give the car a bit more front bite turn in to mid corner.

so yes You are correct
we have done more than swapped springs on installed coilovers. ;-).

I think Option C is a good one Andrew Please PM with price on front springs. Also I would think the compression can be turned down once the spring rate is upped.

After doing so more research I noticed my auto LSD is kicking in. This means one of my rear tires is coming off the ground in certain situations.

If I add spring rate to the front this should keep the rear more planted?
Or should I remove a little spring rate in the rear to help it articulate?
I also could run the front end of the car a tad bit higher than it currently is to get more weight to the rear.

ROBISPEC noticed this behaivior early on in our testing. We solved it by a comb. Of the changes we made. Lowered cofG remove rear sway added rear spring rate.

interesting post:

My take reading it was that your rear is too stiff with your setup in relation to your nose

have you tried a stiffer front sway?

does KW offer only one spring setup with this kit?

I dont think the rebound valving is your issue. What rubber are you running?

do you kno what rates your running currently?
dont go changing rates without attention to bias front to rear, and dont forget your sways affect spring rates when in corners.